It is desirable to be able to feed an entire stack of documents one at a time through a copying machine without hand-feeding, and to have each document returned to the bottom of the stack, so that when the stack has been completely copied, it is in its original order when the stack of documents is removed from the machine. Further, separate trays are not needed to receive the original documents to be copied and those which have been copied, minimizing the overall size of the machine.
It is therefore an objective of this invention to provide an improved recirculating automatic document feeder. More particularly, an objective herein is to provide an automatic document feeder feeding each document in turn from the top of the stack, along a path through the copy machine and returning the document in its original orientation to the bottom of the stack.
A major problem in the design of such a system is that in order to return each copied document to the bottom of the stack, the stack must somehow be lifted once during each copy cycle, after the copy is made, so that the returning document may slide into its place underneath the stack of documents, properly aligned with the complete stack.
It is therefore an objective herein to provide a recirculating document feeder that lifts the stack to be copied by the edge in a timely, sequential fashion so that each returning document slides into its place at the bottom of the document stack, and the stack is then returned to rest on the returned document; in this way, upon completion of the next copy cycle, the complete stack may again be lifted out of the returning document's path.
One problem in such a design is that if the copier and the paper stacker are not perfectly aligned as the sheet moves under the stack, the sheet being returned to the bottom of the stack remains misaligned with the stack. A misaligned sheet may also drag against one side of the frame defining the sides of the paper stack. In this case, the paper will not slide or carry all the way forward to the front paper stop. In fact, the paper will probably skew to one side as it moves under the stack, interfering with the next following paper and clogging the paper return path.
Simply making the entry channel for the paper wider will not solve the problem; the result would be a decrease in the positional accuracy of the stack. An objective herein is to provide means and method for properly aligning each returning piece of paper with the existing stack.